Beneath the cover can be found the newly-developed Citaro NGT gas cylinders. They are made from a composite material with a plastic core, a carbon-fibre sheath and – new – a glass-fibre sheath as well. This combination of materials is extremely lightweight on the one hand, and on the other hand highly robust. The gas cylinders are refilled as standard in the bus's engine compartment. Optionally, the filler necks can be shifted to a position above the right-hand wheel arch. This is the position of the diesel-powered Citaro filler neck.